Enatioselective Study Of Self-prepared Chiral Stationary Phases Of Thio-BINOL With Tartrate As Mobile Phase Additives

Chirality is a basic property of nature,especially living organisms,nucleic acids,polysaccharides and other living substances,all of these have chirality and exist in a single configuration in the body.And using asymmetric compounds,the yield and purity were put forward higher requirements.Currently,the chiral compounds occupied 60%in clinical drugs,and racemic compounds are about 88%to therapy.The consideration of improving drug efficacy,reducing toxicity,improving drug therapeutic index,and reducing interaction between drugs,chiral separation has become a focus problem in academic research and pharmaceutical development.Futhermore,the axial chiral compounds represented by binaphthol（BINOL）have been widely used in fluorescence sensors,chiral catalysis,X-ray diffraction and other chiral recognition fields,and tartrate with two chiral centers have applications too.Considering HPLC is efficient and convenient for chiral resolution,there have been many reports combined BINOL and tartrate in chiral recognition.In this paper,R/S-1,1’-binaphthol（1,1’-binaphthol,BINOL）was used as raw material to prepare two kinds of BINOL with sulfur spacer arm,which were bonded to silica gel surface and obtained two sulfur spacer arm BINOL CSPs,which named（R）-Thio-BINOL CSP,（S）-Thio-BINOL CSP,respectively.In addition,two types total eight of tartrates were prepared with（2R,3R）/（2S,3S）-tartaric acid and different alcohol reagents,then they were used as chiral mobile phase additives（CMPA）to enantioseparate 32 chiral solutes,including amino alcohols,flavanones,1,4-dihydropyridine,using R/S-Thio-BINOL CSP.Furthermore,the force between CSP,CMPA and chiral solutes was calculated by molecular docking.The chiral recognition mechanism of Thio-BINOL CSP and tartretes CMPA was preliminary investigated.Objectives:1.Thio-BINOL-CSP and chiral mobile phase additives（CMPAs）were prepared.2.High performance liquid chromatography was used to enantioseparate 32kinds of chiral solutes,including amino alcohols,flavanones and 1,4-dihydropyridine by self-made Thio-BINOL-CSP and tartrates as chiral mobile additives phases.3.Molecular docking calculation and Pymol visualization analysis were used to preliminary explore the cooperative resolution mechanism of Thio-BINOL-CSP and tartrates CMPAs.Methods:1.Preparation of Thio-BINOL-CSP:（1）Using R/S-BINOL as raw material,thiourea group was introduced into the spacer arm to prepare two configurations of BINOL derivatives.The sulfur spacer BINOL derivatives were bonded to silica gel surface,and get two configurations of sulfur spacer BINOL-CSP,named（R）-Thio-BINOL CSP and（S）-Thio-BINOL CSP.（2）The compounds and stationary phases were characterized by nuclear magnetic resonance（NMR）,liquid chromatography-mass spectrometry（LC-MS/MS）,elemental analysis（EA）,and scanning electron microscopy（SEM）.（3）Different chiral stationary phases were packed into corresponding HPLC columns by high-pressure homogenization method.2.Preparation of chiral mobile phase additives（CMPAs）:two configurations of tartaric acid and a series of alcohol reagents were used as raw materials,and a total of eight tartaric esters compounds were obtained by esterification reaction,and they were used as CMPAs.3.The chiral separation co-work by CSP and CMPA:Binding BINOL CSPs with sulfur spacer arm as stationary phase and tartrates as CMPAs,32 chiral solutes including flavonoids,amino alcohols,dihydropyridines were separated under the polar mobile phase.4.The chiral recognition mechanism investigation:Molecular docking calculation and Pymol visualization analysis were used to preliminary explore the chiral recognition mechanism of Thio-BINOL-CSP,CMPA and chiral solutes based on the chromatographic resultsResults:1.Preparation of CSP:（R）-Thio-BINOL CSP and（S）-Thio-BINOL CSP were prepared,and the structures were characterizated by elemental analysis and scanning electron microscopy.2.Preparation of CMPA:2 configurations containing 8 types chiral mobile phase additives were obtained,and the yield between 70.0%-75.0%3.Chiral solute resolution:With different type of CMPAs.32 kinds of chiral solutes got different degree enantioseperation under polar mobile phase using Thio-BINOL CSPs,（R）-Thio-BINOL CSP can only resolve amino alcohols;Using 1%tartaric propyl esters CMPA,（S）-Thio-BINOL CSP can separate 30 kinds of chiral compounds.4.Molecular docking results:Without addition of CMPA,theΔE_binding between（S）/（R）-Thio-BINOL CSP and metoprolol was 0,the result is that metoprolol was not enantioseparated.After adding 0.5%D-（-）-dipropyl tartaric esters CMPA,theΔE_bindingbetween（S）/（R）-Thio-BINOL-CMPA and metoprolol was 0.49 and 0.80,respectively,so that,the metoprolol enantiomers got separated.Conclusions:1.Under the condition of polar mobile phase and same tartrates CMPAs,,the resolution ability of（S）-Thio-BINOL CSP is better than（R）-Thio-BINOL CSP aiming to 32 chiral solutes.For the（S）-Thio-BINOL CSP,the enantioseparation strength of the CMPAs is descending as follow:propyl ester,isopropyl ester,butyl ester,ethyl ester.For the（R）-Thio-BINOL CSP,the enantioseparation strength of the CMPAs is descending as follow:butyl ester,propyl ester,isopropyl ester,ethyl ester.There is no obvious rule between chiral recognition performance and the configuration,proportion and of the CMPAs.2.The results of molecular docking showed that it is beneficial for possessing van der Waals force,hydrogen bond and solvation energy between CSP-CMPA-metoprolol to chiral separation.